Prior Art
On account of its high quality and productivity, continuous generation grinding of gears is considered to be one of the hard finishing processes, which have also become widespread in the large-scale manufacture of gears. The grinding tool, the so-called grinding worm, is a cylindrical grinding wheel which has at its circumference a rack-like worm-shaped profile, which during grinding can be brought into meshing engagement with the premachined workpiece toothing. The grinding worms are profiled with rotating dressing discs which are coated with hard-material grains, engaged in the grinding worm thread during the dressing and, while in contact with one flank or simultaneously with both flanks of the grinding worm thread, is displaced in accordance with the pitch of the latter parallel to the grinding-wheel axis.
When re-using a grinding worm which is already profiled or when using a new rough-profiled grinding worm, the task of the operator, as a requirement for the subsequent automatic dressing process, is to manually determine the axial position of the existing grinding-worm thread and to accordingly positioning the dressing tool axially. In this case, axial position of the thread center is determined by the dressing tool being fed into the tread of the grinding worm and then being displaced parallel to the grinding worm axis until audible or visible contact with the grinding worm thread flanks occurs. This method is time-consuming and requires skill, since the contact between dressing tool and grinding worm can often only be detected with difficulty because of poor accessibility of the engagement point, and the centering of the dressing tool, on account of the small dressing infeed amount, in particular in the case of CBN grinding worms (abrasive grains of cubic boron nitride), has to be very accurate.